1. Field of the Invention
This invention relates to the fabrication of lasers. More particularly, it relates to fabrication and fine tuning of laser apparatus which utilizes recirculation geometry.
2. Description of the Prior Art
A class of helium-cadmium lasers utilizes cataphoretic transport to define the cadmium vapor density in the laser tube. Cataphoresis, also known as electrophoresis, refers to the movement of suspended particles through a fluid under the action of electromotive force applied to electrodes in contact with the suspension. In the context of lasers, the electromotive force is applied at the anode and cathode electrodes, and the fluid is the helium-cadmium gas in the tube. In accordance with known techniques, helium-cadmium cataphoretic lasers utilize a recirculation geometry, in which a bypass path is provided for cadmium vapor to diffuse back from the cathode to the anode end of the laser tube. Because the cataphoretic flow rate in cadmium lasers is much faster than the diffusion flow rate, the cross-sectional area of the bypass path must be much larger than that of the main discharge bore. In particular, it has been shown that the bypass path should be approximately two orders of magnitude larger than the main bore. Consequently, special precautions are necessary to prevent breakdowns through the return path. In accordance with accepted procedures, baffles arranged along the principle axis of the tube prevent breakdown in the diffusion return line without impeding the vapor flow.
In a typical configuration, a cathode element is located approximately in the center of the laser tube, and anode elements are located at either end. Ceramic tubes which define the main discharge bore are situated on the center axis of the main tube, and grids (i.e., baffle arrangements) are located periodically along the principal axis between the central bore and outer envelope tubes. In particular, the baffle arrangements may be made of honeycomb cylindrical segments, or alternatively as pairs of connected perforated discs. Thus, by the connection of the central bore tube with the outer envelope of the laser, a coaxial vessel is formed, with the metal grids preventing breakdown in the diffusion line but not impeding the vapor flow. Situated at either end of the laser are mirrors which, when properly adjusted along the principal axis of the laser, induce lasing when the helium-cadmium gas is energized by the electrodes.
It is an object of the present invention to provide methods for fabricating cataphoretic lasers.
It is a further object of the present invention to provide methods for fine tuning cataphoretic lasers to achieve effective laser action.